It's unclear whether this was the most necessary of the Slivers, but it was the one that frustrated the most opposing plans to deal with the problem and even opened up new game plans when the card advantage resulting from saving your creatures could allow Sliver decks to go the control route when backed up by counters and removal spells
Niambi comes in, rescues a creature from removal, then starts (slowly) setting up future reanimation like a big ol' Primevals' Glorious Rebirth
Lightning Helix versus Lightning Bolt is no contest, of course, but Ral Zarek has one very major advantage over Ajani Vengeant
Retrieve the Clover Once your pod has played against Gorion a few times, Lucky Clover will likely end up as a target
Not only did these decks never win, I couldnt play a single spell in many of these games
This can stop an attack outright, disrupt their setup, or completely swing tempo in your favor when timed well